Double Bass How to adjust the bridge adjuster wheels for lower action?

[Les Fret]

I have two basses with adjuster wheels (Full Circle) and have used these wheels before. But I am not sure if I am doing it right. I want to have a lower action on one of the basses. What the steps to follow for adjusting the wheels? Which side first E string or G string? and do I have to loosen the string tension or not? and what if I only want to lower the action of the G string side?

A luthier told me that lowering the wheels on the E string side will have a reverse effect on the action of the G string? I am not sure exactly what he meant but is that right?

And one related question: we had a heath wave of a few weeks here but I was on a vacation. When I came back I felt that the action of the strings of that bass had raised. I am not sure though. Maybe it was my imagination or the fact that I didn't play it for 3 weeks. Can heat cause the action to go higher?

 

[Jay Corwin]

Because of how the bridge and board are crowned, if you raise or lower one side independently - it will affect both the position and height of the strings on the opposite side. How much depends on how the bridge was cut. Minor tweeks can be gotten away with, but if you're going to make a significant adjustment it's a good idea to make incremental adjustments to both sides. Keep in mind this might also slightly change the tone of the Full Circle.

Humid summers can swell the bass and raise the string height enough to make it noticeable. Where are you located? Depending on the climate where your at, you might be served to make adjustments periodically. It also depends on the bass. Some are more prone to season changes than others.

The guys who cut bridges here can give you a more detailed explanation.

 

[turf3]

You have to consider the geometry. The bridge, fingerboard, and string pattern are all highly curved and the adjusters are much lower than the strings. If you change the adjustment of only one adjuster, you have about as much sideways movement as vertical. This will create odd effects you hadn't planned for.

The good news is that it's all reversible. Put a mark on each wheel; record (on paper) the height of each string; make and adjustment AND WRITE DOWN EXACTLY WHAT IT WAS; measure AND RECORD the resulting new string heights; and so on.

If for example you want to make different adjustments to the E string compared to the G string, unless the difference is quite minor, you will have great difficulty doing so by adjusting the two wheels differently. In the end you will probably need to shave the relevant string slots (non-reversible, you can always take material off but it's really hard to put it back on) if the diffrernces in the amount of your desired string height change are more than trivial.

I went through all this a couple years ago and ended up deepening one or two string slots on the bridge just a bit. Be careful - in my case I am not afraid of doing this kind of thing but I have confidence in my skills (and I know where those skills end, too!)

 

[misterbadger]

If you lower the E side adjuster, the G string will move laterally toward that side, moving it to a higher point on the fingerboard radius and lowering its height above the board as well.

 

[Les Fret]

Thanks for the input guys!
So it's best to adjust both sides in the same amount then?
And do you loosen the strings when you make adjustments?

 

[turf3]

Thanks for the input guys!
So it's best to adjust both sides in the same amount then?
And do you loosen the strings when you make adjustments?

I don't loosen them when I'm lowering, but my adjusters work real smoothly and easily. I will typically tune down a bit (a couple whole steps, but not more than that) when raising,